Firefighter Lt. Justin Greenhaw said the two runners went to the Southport Fire Department at 5:45 a.m. Monday and alerted the company to the blaze. As the first truck went down Main Street onto Pequot Avenue, firefighters could see smoke rising from the building, Greenhaw said.

Shortly after the call went out, five engines and two ladders were called from Fairfield and an additional engine and ladder from Bridgeport were called to assist in protecting the adjoining buildings, Assistant Fire Chief George Gomola said.

"We're not sure where the fire started," Gomola said. But the blaze expanded up into the ceiling void and spread through the roof of the building, he said.

No other businesses in the building were harmed, he said. The Russell Insurance Agency said it has a firewall between it and the pizzeria. The fire department said there was minimal damage to art in the adjoining art dealership.

It took just over an hour for firefighters to completely extinguish the blaze, Gomola said. There were concerns about the building's structure after it was determined that the rafters and the HVAC system were damaged during the fire, he said.

Firefighters were cleaning the area around the pizzeria by 8:30 a.m., and engines were leaving the scene.

Fairfield police closed off a section of Pequot Avenue between the Post Road and Main Street for firefighters to continue their work.

The cause of the blaze was under investigation by the Fire Marshal's Office.